Reading and writing brain with light

Light has always been a source of inspiration to humans.

'Let there be light', our prophets have long been commanded as.

'Lead me from darkness to light', 

our seers have asked to higher existence since long ago.

And the 2015 has been proclaimed as the 

'International year of light' 

by UN's 68th general assembly.

Optics and photonics have many positive impact in fields 

as diverse as 
energy, eduction, agriculture and health.

As a child
it was bioluminescence of fireflies
which attracted us.

And as a grown up, 
humanity is just finding 

Quantum teleportation ways, 
transforming Energy into matter, 
New light to illuminate the world.

Now reading and writing brain with light.

Holographic targeting of laser beams to individual neurons in the mouse barrel cortex. 
Photograph: Lloyd Russell/Häusser Lab/UCL 
share source: http://www.theguardian.com/science/neurophilosophy/2014/dec/22/researchers-read-and-write-brain-activity-with-light

This is a case of fields combine of
Neurology and Philosophy i.e.

Neurophilosophy.

Neuroscientists of University College London 

have found out that light could be used 

for simultaneous recording and alteration of neurons impulses 

in the living brain.

The technique, described in the journal Nature Methods, combines two existing state-of-the-art neurotechnologies.

One of them is optogenetics. This involves creating genetically engineered mice expressing algal proteins called Channelrhodopsins in specified groups of neurons. This renders the cells sensitive to light, allowing researchers to switch the cells on or off, depending on which Channelrhodopsin protein they express, and which wavelength of light is used. This can be done on a millisecond-by-millisecond timescale, using pulses of laser light delivered into the animals’ brains via an optical fibre.  

The other is calcium imaging. Calcium signals are crucial for just about every aspect of neuronal function, and nerve cells exhibit a sudden increase in calcium ion concentration when they begin to fire off nervous impulses. Using dyes that give off green fluorescence in response to increases in calcium concentration, combined with two-photon microscopy, researchers can detect this signature to see which cells are activated. In this way, they can effectively ‘read’ the activity of entire cell populations in brain tissue slices or live brains. 

High-speed calcium imaging shows
simultaneous activation of six neurons
arranged in the shape of a smiley face.
Credit: Lloyd Russell, Hausser lab, UCL

To demonstrate the precision of the technique, they used a programmable device called a spatial light modulator that splits the light beam into a hologram consisting of smaller ‘beamlets’, and then simultaneously activated six neurons arranged in the shape of a smiley face.
thankfully shared/cited from:http://www.theguardian.com/science/neurophilosophy/2014/dec/22/researchers-read-and-write-brain-activity-with-light 

“We’re excited about this,” says senior author Michael Häusser. “It unites two revolutions in neuroscience and heralds a new era in which we can abandon electrodes and use light alone to probe neural circuits during behaviour.”
Links:
https://www.ucl.ac.uk/news/news-articles/1214/231214-light-brain/ 
http://www.sciencemag.org/content/346/6216/1506
http://www.ucl.ac.uk/wibr

Abstract of article from Nature Methods in original:
(thankfully shared from: http://www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth.3217.html
We describe an all-optical strategy for simultaneously manipulating and recording the activity of multiple neurons with cellular resolution in vivo. We performed simultaneous two-photon optogenetic activation and calcium imaging by coexpression of a red-shifted opsin and a genetically encoded calcium indicator. A spatial light modulator allows tens of user-selected neurons to be targeted for spatiotemporally precise concurrent optogenetic activation, while simultaneous fast calcium imaging provides high-resolution network-wide readout of the manipulation with negligible optical cross-talk. Proof-of-principle experiments in mouse barrel cortex demonstrate interrogation of the same neuronal population during different behavioral states and targeting of neuronal ensembles based on their functional signature. This approach extends the optogenetic toolkit beyond the specificity obtained with genetic or viral approaches, enabling high-throughput, flexible and long-term optical interrogation of functionally defined neural circuits with single-cell and single-spike resolution in the mouse brain in vivo.
http://www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth.3217.html 

Figure: Simultaneous fast calcium imaging and concurrent photostimulation of multiple neurons in vivo.thankfully shared from: http://www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth.3217.html